Originally Posted by Daffietje
He also mentioned the White was not clipping but the CMS was/is above IRE90.
So lowering the contrast value on the Oppo was not to prevent the Oppo from clipping the White (because the Oppo is not doing that) but to prevent the Oppo from clipping the CMS above the IRE90 range.
I just checked this again in my setup with my test 103, and I don't see any such clipping.
Tested with Spears & Munsil v2, Blu-ray > Advanced Video > Setup. In this section of this calibration disc there are 6 charts that display the high Luma end of the video data. These are Contrast Y (i.e., Luma), Contrast Cb, Contrast Cr, Contrast Red, Contrast Green, and Contrast Blue.
All 6 display the given data channel as individual, labeled bars for Luma 231 through 253 against a background of Luma 254. There's also a double ramp used to check for quantization (rounding) errors.
(For newbies: Reference White has a Luma value of 235, and of course no color. The Luma values from 236 to 254 are the Peak White values. 255 is a reserved value. The pixel data on disc is in YCbCr format where the Y component is the Luma or gray scale brightness of the pixel, and the Cb and Cr components are the Blue and Red "color difference" values describing how much blue/red to add or subtract to that gray scale brightness to color the pixel. E.g., take all the Blue and Red out of a white pixel and you end up with a Green pixel. YCbCr format can be converted to RGB format -- Red, Green, and Blue component values for each pixel. A gray pixel anywhere in the range from Black to White would then be a pixel that has equal values for R, G, and B.)
In all 6 charts, I can see the data bars up to 253, which is correct. Of course the bars near 253 are tougher to see as they are closer to blending into the Luma 254 background. Check this in a darkened room with eyes adapted. So: No clipping in either whites or colors.
The 103 is running the Official 0515 firmware. I'm using HDMI 1, set to output 1080p/24 using YCbCr 4:4:4 and Deep Color OFF (Dithered). The Dithering in the player is needed for the way I use my Display.
NOTE: All this really proves is that the individual values up there really are present on the HDMI cable -- i.e., the OPPO is not clipping, say, values above 245 to 245. The Gamma of these high Luma values may or may not be correct. But that's a Display calibration issue, not an issue with the output of the OPPO.
Now, it is not at all unusual for *A DISPLAY* to clip one or more color channels at high Luma. For example, the Display might be able to show Blue distinguishable up to only Luma 245, even though Red and Green don't clip. One symptom of this is that high Luma value White bars start to develop a color tinge because, in this example, the Blue is only going up so high.
The way to check if THIS is the problem is to reduce white levels (i.e., using the Contrast control) in the Display (*NOT* in the OPPO). The higher Luma value bars should start to become visible -- which also demonstrates that the player itself is not doing the clipping, because those bars are there, on the HDMI Cable, to view if only the Display could handle them.
In such displays, there's a trade off that has to be made for the Display's own Contrast setting. Lowering the Display's Contrast setting lowers dynamic range (i.e., maximum image brightness). As long as there is no Clipping up to Reference White in any color channel you can live with that. If there is clipping (in the Display) above Reference White, you can lower the Display's Contrast setting to reduce that, but only so far as still leaves you with a pleasing appearance for Reference White -- i.e., not gray or dingy. This can be quantified in terms of recommended light level for Reference White (for your type of Display) if you use an optical sensor.